WO2001076123A1 - Estimating communication quality - Google Patents
Estimating communication quality Download PDFInfo
- Publication number
- WO2001076123A1 WO2001076123A1 PCT/IB2001/000628 IB0100628W WO0176123A1 WO 2001076123 A1 WO2001076123 A1 WO 2001076123A1 IB 0100628 W IB0100628 W IB 0100628W WO 0176123 A1 WO0176123 A1 WO 0176123A1
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- WIPO (PCT)
- Prior art keywords
- indication
- error rate
- communications
- transmitter
- receiver
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
Definitions
- This invention relates to estimating communication quality, for example to improving estimation of error rates in received data.
- the invention is preferably suitable for use in a telecommunications system such as a cellular radio telecommunications network.
- FIG. 1 shows schematically the configuration of a typical cellular radio telecommunications network such as a GSM (Global System for Mobile Communications) system.
- the network comprises a number of base transmission stations (BTSs) 1 , 2, 3.
- Each base-station has a radio transceiver capable of transmitting radio signals to and receiving radio signals from the area of a cell 4, 5, 6 etc. next to the base-station.
- the base-station can communicate with a mobile station (MS) terminal 7 in that cell, which itself includes a radio transceiver.
- MS mobile station
- Each base station is connected via a base station controller 8 to a mobile switching centre (MSC) (not shown), which is linked in turn via a gateway MSC 9 to the public telephone network 10 and/or to other networks such as packet data networks.
- MSC mobile switching centre
- the signals between a BTS and an MS carry digital data.
- Analogue voice data to be carried over the link is encoded into digital data using a suitable speech codec.
- the encoded data is then allocated to time slots and transmitted in those time slots to the recipient unit.
- a group of consecutive time slots e.g. 8 time slots in the GSM system
- TDMA frame is made up of 8 consecutive time slots.
- Up to 8 different users at full data rate can be allocated to a single TDMA frame, each user having its own time slot.
- a slot may alternatively be shared between two users at half data rate, in which case those users are allocated the same timeslot but in alternate TDMA frames.
- a user's speech data is carried in the frames allocated to that user. If the user is a full data rate user then a speech frame of the user will occupy one timeslot of eight consecutive TDMA frames: for example if a TDMA frame lasts for 4,615 ms (as in GSM), one speech frame will taking 8 x 4,615 ms to be fully sent. If the user is a half data rate user his speech frame contains half as much data as that of a full rate user, and occupies one timeslot of four alternate TDMA frames. Thus in GSM the total time taken to transmit a half rate speech frame is essentially the same as the time taken to transmit a full rate speech frame.
- the data is decoded to regenerate the analogue voice data.
- Figure 2 illustrates schematically the receiver path in the mobile station. (The considerations at the BTS are analogous). Incoming received data at 20 is passed to a decoder 21. The decoded analogue voice signals are passed to an output unit 22.
- the quality or error rate of the link is estimated by measuring characteristics of the received signal.
- a bit error rate (BER) before channel decoding can be estimated for the received digital bitstream, as indicated schematically at 23.
- the bit error rate represents the ration of badly received bits to the total number of received bits.
- the decoder 21 can detect badly received voice data frames. This allows a frame erasure rate (FER) to be determined, as indicated schematically at 24.
- FER frame erasure rate
- the frame erasure rate represents the percentage of received frames being dropped due to a high number of non-corrected bit errors in the frame.
- Other methods can be used to determine whether a received frame is to be considered as bad.
- the BER before channel decoding is high the frame could automatically be assumed to be bad, even if the CRC would indicate that the frame was acceptable. This is especially significant in normal full rate data reception, where the CRC occupies three bits, so even if plain noise were sent one in eight frames could on average be taken to be a valid frame
- the BER before channel decoding is estimated and that estimate reported to a control unit which can control the system so as to maintain adequate link quality, for example by instructing an increase or decrease in transmission power or a handover of an MS to another BTS.
- the estimated BER before channel decoding is a direct indication of the level of errors over the link and has therefore been used in prior systems as an indication of the quality of the link on which to base such control measures.
- the conventional GSM system only one voice codec, or only very few codecs, have been available. Therefore, in many cases the relationship between BER before channel decoding and perceived link quality has been easily predictable, although problems exist for example between frequency hopping and non-hopping channels.
- variable compression ratios and alternative error correction techniques such as AMR (adaptive multi- rate), GPRS (general packet radio sen/ice) and EGPRS (extended GPRS) or +ECSD equivalents - the BER becomes a less accurate indicator of true link quality, because the true quality of received voice data as perceived by a user is also dependant on the level of compression and/or error correction that can be performed under the protocols in use over the link. As the proportion of received bits used for error correction increases relative to those used for encoded voice data the potential for efficient error correction increases and BER before channel decoding becomes less accurate as an indicator of link quality.
- AMR adaptive multi- rate
- GPRS general packet radio sen/ice
- EGPRS extended GPRS
- the conventional quality measure is based on the pseudo bit-error rate (pseudoBER) or an estimate of the BER made before channel decoding, which is an estimate of the bit errors over the air interface.
- the (pseudo) BER is calculated before channel decoding. While the robustness against channel errors in AMR operations depends on the codec mode in use, the real performance of the connection cannot be estimated from RxQual alone: knowledge of the codec mode in use is needed. Moreover, since the theoretical maximum link adaptation rate of AMR is 1/40ms, the codec mode can change several (up to a maximum of 12) times during the normal measurement period of GSM (480 ms). This means that the actual BER (after channel decoding) (and FER) of the connection depends on the raw bit error rate of each traffic channel (TCH) frame during the connection and the codec modes used in those frames.
- TCH traffic channel
- the correct quality information is especially important for handover and power control algorithms where one of the most important criterion to increase or decrease the transmit powers or trigger the handovers is the quality of the connection.
- Figure 3 illustrates AMR codec modes.
- An example of simulation results where the most robust codec mode of AMR was used is shown in figure 4. Note that while the connection quality was in lowest RXQUAL class for several seconds during the simulation, the amount of actual frame erasures was still acceptable. In normal FR connection this would have meant a significant break in the speech or even a dropped call.
- One option to provide a more accurate measure of quality would be to send measured uplink FER information from BTS to BSC. However, this would only address the quality measurement problems of the uplink because downlink FER is not available in current GSM systems. This is especially significant since the downlink is normally considered to be the limiting path in terms of interference.
- Another option would be to use the normal RXQUAL measure in handover and power control and to set the RXQUAL thresholds according, for example, to the performance of signaling channels. This would however mean a compromise in the performance tuning of AMR especially if only high modes of the AMR were used.
- a method for estimating quality of communications between a transmitter and a receiver over a communications link operable to carry data in at least one of a plurality of different compressed forms comprising: detecting an error rate of the communications as received; receiving at a quality estimation unit an indication of the detected error rate and an indication of the at least one of the plurality of compressed forms in use over the link; and the quality estimation unit estimating the quality of the communications by means of both the indication of the detected error rate and the indication of the at least one of the plurality of compressed forms.
- a communications system comprising: a transmitter and a receiver capable of communicating over a communications link operable to carry data in at least one of a plurality of different compressed forms; error rate detection apparatus for detecting an error rate of the communications as received; and a quality estimation unit for receiving an indication of the detected error rate and an indication of the at least one of the plurality of compressed forms in use over the link, and estimating the quality of the communications by means of both the indication of the detected error rate and the indication of the at least one of the plurality of compressed forms.
- a network element for operation in a communications system in which a transmitter and a receiver can communicate over a communications link operable to carry data in at least one of a plurality of different compressed forms;
- the network element comprising: a transmitter or a receiver capable of communicating over a communications link operable to carry data in at least one of a plurality of different compressed forms; error rate detection apparatus for detecting an error rate of the communications as received; and a quality estimation unit for receiving an indication of the detected error rate and an indication of the at least one of the plurality of compressed forms in use over the link, and estimating the quality of the communications by means of both the indication of the detected error rate and the indication of the at least one of the plurality of compressed forms.
- the data is preferably speech data, but could be other data such as video data or text data.
- the data is suitably carried in digital form.
- the different compressed forms are suitably forms resulting from compression by different codecs.
- Those codecs may together form a multi-rate coding scheme.
- the multi-rate coding scheme may involve the selection from time to time of one of the codecs from the set on the basis of detected conditions of the link.
- the error rate may be an estimation of bit error rate, preferably before channel decoding, or a pseudo bit error rate. Other measures of error rate may be used, especially in systems other than the GSM system.
- One of the transmitter and the receiver may be a base transmission station.
- the base transmission station may be under the control of a base station controller.
- the other of the transmitter and receiver is a mobile station.
- the receiver unit may also be capable of transmitting signals to the transmitter, which may be capable of receiving them.
- the quality estimation unit may be located at the base station controller.
- the link may be a traffic channel.
- the link may be part of a radio communications channel between the transmitter and the receiver, which may also include control channels.
- the indication of the detected error rate suitably includes information indicative of a detected error rate for communications over the link from the transmitter to the receiver (and suitably from the receiver to the transmitter).
- Data over the link is sent in the form of data frames and the indication of the detected error rate includes a value of error rate for each frame for communications from the transmitter to the receiver, and an average value of error rate for a plurality of frames for communications from the receiver to the transmitter.
- the receiver is a mobile station and the transmitter is a base transmission station.
- the indication of the detected error rate includes an average value of error rate for a plurality of frames for communications from the transmitter to the receiver.
- Suitably data over the link is sent from the transmitter to the receiver in the form of data frames and the indication of at least one of the plurality of compressed forms comprises an indication of one of the forms for each of the frames.
- Data over the link may be sent from the transmitter to the receiver in the form of data frames and the indication of at least one of the plurality of compressed forms comprises an indication of one of the forms for only some of the frames.
- the data over the link is sent from the transmitter to the receiver in the form of groups of data frames and the indication of at least one of the plurality of compressed forms comprises an indication of one of the forms for the first frame of each group and an indication of one of the forms for the last frame of each group.
- the groups may be multiframes.
- the frames may be sent in one or more TDMA frames. Each TDMA frame preferably occupies 4.615ms. For example, in the GSM system TDMA frame is made up of 8 consecutive time slots.
- Up to 8 different users at full data rate can be allocated to a single TDMA frame, each user having its own time slot.
- a slot may alternatively be shared between two users at half data rate, in which case those users are allocated the same timeslot but in alternate frames.
- a user's speech data is carried in the frames allocated to that user. If the user is a full data rate user then a speech frame of the user will occupy one timeslot of eight consecutive TDMA frames: for example if a TDMA frame lasts for 4,615 ms (as in GSM), one speech frame will taking 8 x 4,615 ms to be fully sent.
- Each group of frames preferably comprises 24 frames, or 26 frames including traffic and control frames.
- the data over the link is suitably sent from the transmitter to the receiver in the form of groups of data frames and the indication of at least one of the plurality of compressed forms comprises an indication of one of the forms for a single frame of each group. .
- the groups may be multiframes.
- Each group of frames preferably comprises 24 frames, or 26 frames including traffic and control frames.
- Each group of frames suitably corresponds to a measurement period.
- the said averaging of error rates is preferably performed over that period, or over a longer period.
- the method may comprise the step of limiting the transmitter and the receiver to using a single one of the compressed forms over the link in each measurement period, which may be a multiframe.
- the transmitter and the receiver are preferably operable according to the Global System for Mobile Communications or a derivative thereof.
- figure 1 shows schematically a cellular network
- figure 2 illustrates data reception
- figure 3 illustrates AMR codec modes
- figure 4 shows simulated results of a the correlation between BFI and RxQual value (for FIXED codec mode: 4.75 kbit/s, dynamic channel profile "es11", full-rate channel, GSM downlink);
- figure 5 is a schematic diagram of relevant parts of a GSM cellular network.
- AMR GSM Adaptive Multi-Rate
- ETSI European Telecommunications -Standards Institute
- HR half-rate
- the ETSI AMR codec concept is intended to be capable of adapting its operation optimally according to the prevailing radio channel conditions.
- the quality of the transmission is measured. Since the control of the used codec mode (source coding vs. channel coding bit-rate) is performed by the BTS, the mobile station is only able to send requests of appropriate downlink (DL) codec mode, which may be overwritten by the system. These requests are sent in-band in the uplink (UL) channel.
- the control of the UL codec mode by the BTS is based on quality measurements performed by the mobile station and/or the BTS itself.
- the BTS forces the mobile to use an appropriate codec mode by means of a codec mode command sent in-band on the downlink to mobile station.
- a codec mode command sent in-band on the downlink to mobile station.
- an indication of the codec mode(s) in use on the uplink and/or the downlink is sent to the BSC.
- the BSC can perform handover and power control calculations, mapping the RXQUAL into a more realistic quality estimate, which may represent a frame erasure probability (FEP).
- FEP frame erasure probability
- each multiframe provides 26 frames, of which a group of 24 frames are allocated for carrying traffic speech data for one user, and may therefore carry data encoded according to a selected speech codec.
- Signaling capacity limitations on the Abis interface mean that there are several possibilities for conveniently sending the necessary information to the BSC.
- the BSC would be sent information indicating: a) the codec used for each one of the 24 traffic channel frames on the uplink; b) the codec used for each one of the 24 traffic channel frames on the downlink; c) a RXQUAL (BER before channel decoding) value for each of the 24 traffic channel frames on the uplink; d) an average RXQUAL value for a plurality of frames of the downlink - preferably the 24 traffic frames of a single multiframe; (the RXQUAL of each individual DL frame is not available).
- the BSC would be sent for the uplink or the downlink or both, information indicating: a) the codec used in the first and last of the traffic channel frames of a multiframe; b) RXQUAL information averaged over a measurement period (which could suitably be the period of a multiframe).
- the AMR scheme could be restricted so that link adaptation occurs only every 1 /480ms, between multiframes. This would have the effect that the codec in use would remain constant throughout a multiframe.
- the BSC would be sent information indicating: a) the codec mode in use during the multiframe; and b) RXQUAL information averaged over a measurement period (which could suitably be the period of a multiframe).
- the first route offers the best accuracy combined with the most flexible link adaptation (there being no restrictions on link adaptation rate).
- the third route is able to give the same accuracy in quality assessment, but the ability to react fast to changes in the channel is worse since the operation of the AMR system is restricted. Simulations performed by the applicant have indicated that this factor is generally not critical to performance: route 3 was able to offer even better link performance in certain simulations, especially in half rate mode. The reason for this is believed to be that in some cases the link was adapted even too aggressively in fast link adaptation while the actual link quality had already changed to opposite direction.
- the first route consumes a significant amount of Abis signaling capacity, which may easily cause problems if the additional TRX-signaling is not taken into account in network planning.
- the second route offers a compromise in terms of quality estimation accuracy, as the actual quality has to be estimated as an average over used codec modes together with the RXQUAL information.
- the BSC When the BSC has the knowledge of used codec modes and the RXQUAL associated to those modes, it can use a simple mapping table to convert the RXQUAL values into real connection quality or FEP, which can be used for example as a trigger in handover and power control algorithms.
- Figure 5 illustrates the architecture of a GSM system for implementing a preferred embodiment of the invention.
- Figure 5 shows a mobile station 40 in radio communication with a base transmission station 41 over a wireless link 42.
- the antennae 43, 44 of the mobile station and the BTS are connected to respective duplexers 45, 46 which combine the incoming and outgoing signals.
- the generation of the outgoing signals for transmission is not illustrated in figure 5.
- the incoming signals are passed to respective amplification and demodulation units 47, 48 which derive received digital bitstreams at 49, 50.
- the received bitstream is processed by decoding apparatus shown generally at 51 to decode the data and derive an analogue speech signal at 52.
- the speech signal is applied to a loudspeaker 53 so that it can be heard by a user.
- the received digital signal at 50 is transformed into a signal suitable for onward transmission to BSC 54 by means of processing unit 55.
- the transmission power used over the link 42, the codec used for speech transmission over link 42, the estimated RXQUAL for link 42 and other parameters such as handover operations are under the control of a unit such as BSC 54. These parameters are transmitted from that control unit via link 56 to the respective MS and BTS units to allow them to encode, transmit and decode their signals accordingly.
- the units 51 and 55 are respective error rate detectors 57, 58 which determine error rates (suitably BER before channel decoding (including pseudo bit-error rates) or frame erasure rates) for received signals.
- error rates suitably BER before channel decoding (including pseudo bit-error rates) or frame erasure rates
- the mobile station does not have to calculate any statistical value of the frame errors (e.g. rate); instead the mobile could check the speech frames - frame by frame - and if a frame were found to have too many errors it could be not directed to the audio equipment of the mobile station. In that case the unit 51 could be omitted.
- the error rate data is reported, together with data indicating the codec(s) in use (for example, as in one of the reporting routes discussed above) to the control unit - in this example BSC 54.
- the BSC 54 includes a handover/power-control processing unit 59 which uses that data to determine whether a modification of the communications operations between the BTS and the MS is needed.
- a modification may take the form of an increase or decrease in target RXQUAL (which may result in an increase or decrease in transmission power over the link between the BTS and the MS) or hard and/or soft handover commands to cause the MS to communicate with another base station.
- the BSC can make better decisions on the adjustment of RXQUAL targets, reducing the risk of RXQUAL being increased when high bit-error rates are being at least partly compensated for by compression schemes with high levels of redundancy, or being reduced when even low bit-error rates are being inadequately compensated for by compression schemes with low levels of redundancy.
- the calculations may be performed by another unit than the BSC - for example an MSC.
- the approaches described above may be applied individually to the uplink or to the downlink, or to both.
- the approaches described above may be implemented in telecommunications systems operable according to other systems and standards, for example the third generation (3G) standard.
- the MSC rather than the BSC, could handle handover and power control analysis. Reporting of data to the MSC could be performed over the lu interface.
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- Engineering & Computer Science (AREA)
- Quality & Reliability (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
- Radio Transmission System (AREA)
- Detection And Prevention Of Errors In Transmission (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Monitoring And Testing Of Transmission In General (AREA)
Abstract
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Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
BR0109822-5A BR0109822A (en) | 2000-04-03 | 2001-04-03 | Method for estimating communications quality between a transmitter and a receiver over a communications link, communications system, and network element for oppression in a system and communications. |
DE60141004T DE60141004D1 (en) | 2000-04-03 | 2001-04-03 | ESTIMATION OF THE COMMUNICATION QUALITY |
JP2001573676A JP3710420B2 (en) | 2000-04-03 | 2001-04-03 | Estimating communication quality |
AT01917405T ATE454761T1 (en) | 2000-04-03 | 2001-04-03 | ESTIMATE COMMUNICATION QUALITY |
US10/240,672 US7177593B2 (en) | 2000-04-03 | 2001-04-03 | Estimating communication quality |
AU2001244481A AU2001244481A1 (en) | 2000-04-03 | 2001-04-03 | Estimating communication quality |
EP01917405A EP1269677B1 (en) | 2000-04-03 | 2001-04-03 | Estimating communication quality |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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GBGB0008119.0A GB0008119D0 (en) | 2000-04-03 | 2000-04-03 | Estimating communication quality |
GB0008119.0 | 2000-04-03 |
Publications (1)
Publication Number | Publication Date |
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WO2001076123A1 true WO2001076123A1 (en) | 2001-10-11 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/IB2001/000628 WO2001076123A1 (en) | 2000-04-03 | 2001-04-03 | Estimating communication quality |
Country Status (10)
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US (1) | US7177593B2 (en) |
EP (1) | EP1269677B1 (en) |
JP (1) | JP3710420B2 (en) |
CN (2) | CN1428027A (en) |
AT (1) | ATE454761T1 (en) |
AU (1) | AU2001244481A1 (en) |
BR (1) | BR0109822A (en) |
DE (1) | DE60141004D1 (en) |
GB (1) | GB0008119D0 (en) |
WO (1) | WO2001076123A1 (en) |
Cited By (4)
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EP1563631A2 (en) * | 2002-11-08 | 2005-08-17 | Interdigital Technology Corporation | Composite channel quality estimation techniques for wireless receivers |
US7082299B2 (en) | 2001-03-16 | 2006-07-25 | Nokia Corporation | Testing loops for channel codecs |
US7227888B2 (en) | 2001-03-16 | 2007-06-05 | Nokia Corporation | Testing loops for channel codecs |
WO2008018740A1 (en) * | 2006-08-07 | 2008-02-14 | Samsung Electronics Co., Ltd. | Method and apparatus for estimating signal quality bitmap for cells |
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SE0401669D0 (en) * | 2004-06-24 | 2004-06-24 | Ericsson Telefon Ab L M | Method and system for saving bandwidth |
KR101471563B1 (en) * | 2008-07-10 | 2014-12-11 | 삼성전자주식회사 | Method and apparatus for per frame based resource sharing in cognitive radio communication system |
US8275406B2 (en) * | 2009-04-30 | 2012-09-25 | Telefonaktiebolaget L M Ericsson (Publ) | Integrated power control and link adaptation |
CN101873185B (en) * | 2010-06-24 | 2014-11-05 | 惠州Tcl移动通信有限公司 | Sensitivity testing method, device and detection equipment of GSM (Global System for Mobile Communications) communication terminal |
CN112486013B (en) * | 2020-11-06 | 2023-04-14 | 北京明瑞之光科技有限公司 | Multi-node control system, regional wireless time service device thereof and landscape lighting system |
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- 2001-04-03 CN CN01808831.7A patent/CN1428027A/en active Pending
- 2001-04-03 AU AU2001244481A patent/AU2001244481A1/en not_active Abandoned
- 2001-04-03 EP EP01917405A patent/EP1269677B1/en not_active Expired - Lifetime
- 2001-04-03 BR BR0109822-5A patent/BR0109822A/en not_active Application Discontinuation
- 2001-04-03 AT AT01917405T patent/ATE454761T1/en not_active IP Right Cessation
- 2001-04-03 JP JP2001573676A patent/JP3710420B2/en not_active Expired - Fee Related
- 2001-04-03 DE DE60141004T patent/DE60141004D1/en not_active Expired - Lifetime
- 2001-04-03 US US10/240,672 patent/US7177593B2/en not_active Expired - Lifetime
- 2001-04-03 WO PCT/IB2001/000628 patent/WO2001076123A1/en active Application Filing
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US7082299B2 (en) | 2001-03-16 | 2006-07-25 | Nokia Corporation | Testing loops for channel codecs |
US7227888B2 (en) | 2001-03-16 | 2007-06-05 | Nokia Corporation | Testing loops for channel codecs |
EP1563631A2 (en) * | 2002-11-08 | 2005-08-17 | Interdigital Technology Corporation | Composite channel quality estimation techniques for wireless receivers |
EP1563631A4 (en) * | 2002-11-08 | 2006-08-02 | Interdigital Tech Corp | Composite channel quality estimation techniques for wireless receivers |
WO2008018740A1 (en) * | 2006-08-07 | 2008-02-14 | Samsung Electronics Co., Ltd. | Method and apparatus for estimating signal quality bitmap for cells |
Also Published As
Publication number | Publication date |
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CN101321048A (en) | 2008-12-10 |
JP2003530011A (en) | 2003-10-07 |
ATE454761T1 (en) | 2010-01-15 |
CN101321048B (en) | 2011-04-13 |
GB0008119D0 (en) | 2000-05-24 |
EP1269677B1 (en) | 2010-01-06 |
DE60141004D1 (en) | 2010-02-25 |
EP1269677A1 (en) | 2003-01-02 |
AU2001244481A1 (en) | 2001-10-15 |
BR0109822A (en) | 2003-01-21 |
US20030176184A1 (en) | 2003-09-18 |
JP3710420B2 (en) | 2005-10-26 |
CN1428027A (en) | 2003-07-02 |
US7177593B2 (en) | 2007-02-13 |
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